The invention pertains to a pistol-type syringe having a cylindrical holder for a cylindrical ampoule, a handle with a pivotal actuating lever and a pressure plunger connected with the actuating lever and guided coaxially in the holder, for the displacement of a piston contained in the cylindrical ampoule.
Pistol-type syringes of this type are known in various embodiments. To illustrate the state of the art, reference is made to German Offenlegungsschrift No. 23 58 838, corresponding to U.S. Pat. No. 3,905,365.
In syringes of this type, certain technical difficulties are caused by the transmission of force between the actuating lever and the pressure plunger, since this force transmission operates not only in the manner of a one-way clutch, but must also make possible a transition between the pivoting motion of the actuating lever and the linear movement of the plunger. In the known solutions to this problem, in most cases a tooth arrangement or grooving is provided on the plunger, which is engaged primarily by a movable connecting element fastened to the actuating lever. Such a tooth arrangement or grooving renders impossible an absolutely continuous (i.e., without steps) action by the driving force applied by the actuating lever at any arbitrary point of the plunger.
Furthermore, pistol-type syringes of the above-described type require a braking device to prevent the return of the pressure plunger upon the release of the actuating lever, as a result of the internal pressure of the cylindrical ampoule. Heretofore, mostly simple friction brakes have been used, the braking action of which naturally decreases to a significant degree with progressive wear.
It is desirable to be able to observe the process taking place within the cylindrical ampoule, i.e., in particular the movement of the piston within the cylindrical ampoule, from the outside through a window of the holder. On the other hand, cylindrical ampoules which consist of relatively thin glass or a synthetic material burst with relative ease, when excessive pressure is applied to them by means of the actuating lever, so that the injection solution contained in the ampoule escapes through the window, together with fragments of the ampoule.